Optical head unit for an optical disk using a diffraction gratin

Details Optical head unit for an optical disk using a diffraction gratin Optical head unit for an optical disk using a diffraction gratin

1995-09-15

1997-04-08

Tran, Thang V.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4414, 369103, 369 4441, G11B 709

Patent

active

056194820

ABSTRACT:
An optical information recording-and-reproducing unit includes a diffraction section provided with a reflected optical beam reflected on a storage medium. The diffraction section has at least first and second areas, and from each of the first and second areas, a +1-order diffraction light and a -1-order diffraction light are produced. The unit further includes first and second optical detection sections respectively provided with one of a pair of +1-order diffraction lights and a pair of -1-order diffraction lights produced from the first and second areas of the diffraction section. The unit still further includes a first circuit section for generating a tracking error signal based on output signals of the first and second optical detection sections. In the unit, the light provided to the first optical detection section forms a first spot in a far-field state before convergence, and the light provided to the second optical detection section forms a second spot in a far-field state after convergence.

REFERENCES:
patent: 5243583 (1993-07-01), Ohuchida et al.
patent: 5406543 (1995-04-01), Kobayashi et al.
patent: 5436876 (1995-07-01), Yokoyama et al.
patent: 5475670 (1995-12-01), Hamada et al.

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